Hydraulic device

ABSTRACT

A hydraulic motor-pump assembly including a housing, a chamber formed in the housing, a shaft journaled in the housing and extending into the chamber and a gear set in the chamber including an externally toothed rotor mounted fast on the shaft and an internally toothed stator assembly surrounding the shaft in meshing relation. The stator assembly is geared to the housing so as to cause, in response to relative rotation of the rotor, orbital movement of the stator assembly about the axis of the rotor and rotational movement of the stator assembly about its own axis at a speed less than the speed of rotation of the rotor. Certain passages, ports and the like are provided in the housing and in the stator assembly for directing high- and low-pressure fluid to and from the expanding and contracting fluid pockets formed between the teeth of the stator assembly in a manner providing high operating efficiency. The motor-pump assembly has wide application including use in a vehicular hydraulic motor drive arrangement.

United States Patent [72] Inventors Raymon L. Golf;

Fredrick D. Venable, both of Lafayette, Ind.

[21] Appl. No. 841,405

[22] Filed July 14, 1969' [45] Patented Dec. 14, 1971 [73] Assignee TRWInc.

Cleveland, Ohio 54] HYDRAULIC DEVICE 3,443,378 5/1969 Monroe et a1.103/130 3,452,680 7/1969 White, .Ir. 103/126 A 3,490,383 1/1970 Parrett..T 103/130 Primary Examiner-Carlton R. Croyle Assistant Examinen-WilburJ. Goodlin Attorney-Hill, Sherman, Meroni, Gross & Simpson ABSTRACT: Ahydraulic motor-pump assembly including a housing, a chamber formed inthe housing, a shaft journaled in the housing and extending into thechamber and a gear set in the chamber including an externally toothedrotor mounted 1 fast on the shaft and an internally toothed statorassembly surrounding the shaft in meshing relation. The stator assemblyis geared to the housing so as to cause, in response to relativerotation of the rotor, orbital movement of the stator assembly about theaxis of the rotor and rotational movement of the stator assembly aboutits own axis at a speed less than the speed of rotation of the rotor.Certain passages, ports and the like are provided in the housing and inthe stator assembly for directing highand low-pressure fluid to and fromthe expanding and contracting fluid pockets formed between the teeth ofthe stator assembly in a manner providing high operating effciency. Themotor-pump assembly has wide application ineluding use in a vehicularhydraulic motor drive arrangement.

PATENTEU BECI4I97I 3 321 454 SHEET 1 OF 8 HYDRAULIC DEVICE BACKGROUND OFTHE INVENTION This invention relates generally to the field of hydraulicmotor-pump assemblies and more particularly to such assemblies whichinclude a pair of gears conveniently referred to herein as gerotorgears.

A gerotor gear set includes an externally toothed rotor and aninternally toothed stator which surrounds the rotor in meshing relation.The rotor generally has one less tooth than does the stator and theteeth of both gears are so configured that in response to relativerotation of the gears the axis of one will orbit about the axis of theother. This relative rotational and orbital movement of the gears causessequentially alternately expanding and contracting fluid pockets to beformed between the teeth of the stator.

A rotatable work input-output shaft is connected to a rotatable one ofthe gerotor gears, and when the assembly is used as a motor,high-pressure fluid is directed to the expanding fluid pockets andlow-pressure fluid is directed from the contracting fluid pockets,thereby causing rotation of the shaft. Correspondingly, when'theassembly is used as a pump, the shaft itself is rotated, thereby drawinglow-pressure fluid to the expanding fluid pockets and expelling higherpressure fluid from the contracting fluid pockets.

Fluid is directed into and out of the expanding and contracting pocketsby virtue of valve means which may include one or both of the gerotorgears. The valve means operates in timed relation to the movement of thegears and for that reason may be referred to conveniently as commutationmeans.

Numerous arrangement of gerotor gear sets are known in the prior art. Insome arrangements the stator is held stationary while the rotor bothrotates and orbits. In other arrangements the rotor remains stationarywhile the stator both rotates and orbits. In still other arrangementsone of the gears rotates while the other orbits.

In all of these arrangements the commutation means must be effective todirect the fluid into and out of the expanding and contracting fluidchambers in timed relation with the movement of the gears.

Gerotor gear sets and hydraulic pump-motor assemblies which incorporatesuch gear sets may be more suitable for certain applications than forothers. The motor-pump assembly of the present invention, for example,has particular utility in the field of vehicular drive mechanisms as aresult of its high torque and high operating efficiency capabilities.

SUMMARY OF THE INVENTION The present invention may be summarized ascomprising a hydraulic motor-pump assembly which includes a gerotor gearset constructed and arranged so that the axis of the rotor remainsaligned with the axis of the work inputoutput shaft while the statorassembly rotates relative to the rotor and the axis of the statorassembly orbits about the axis of the rotor. The commutation meansincludes the stator assembly in which certain passages, ports and thelike are formed to direct the fluid into and out of the expanding andcontracting fluid pockets in timed relation to the relative movement ofthe gerotor-gears. The stator assembly is geared to the housing of themotor-pump assembly in a manner whereby the stator assembly rotatesrelative to the housing at a speed much less than the orbital speed ofthe stator assembly, as will be understood by those skilled in the art.

The commutation means provides what is referred to herein asphase-shift" commutation. By the term phase-shift is meant that thecontrol of commutation of highand low-pressure fluid with the expandingand contracting fluid pockets is accomplished by controlling the openingand closing of fluid flow ports located respectively, relative to theaxis of the rotor, in angularly offset relation to the fluid pocketsinto and out of which they control the flow of fluid.

An object of the present invention is to provide a highly efficient,high torque hydraulic motor-pump assembly that is relatively inexpensivein manufacture, has utility in a wide variety of applications and isparticularly suited in vehicular fluid motor drive arrangements.

In such vehicular drive applications the housing of the assembly may bemounted fast to the frame of the vehicle and the wheel mounted for jointrotation on the work output shaft. On the other hand, the shaft may beconnected fast to the vehicle frame and the wheel connected in fixedassembly to the housing of the assembly. The former application isparticu larly suited for higher vehicular speed whereas the latterapplication is particularly suited for higher torque, lower speedapplications.

Several embodiments of a stator assembly constructed in accordance withthe principles of the present invention are illustrated herein. Each ofthese embodiments may have particular utility in certain applicationsand may advantageously utilize different modes of construction andfabrication.

Other objects, features and advantages of the present invention will bereadily apparent from the following description of certain preferredembodiments thereof, taken in conjunction with the accompanying drawing,although variations and modifications may be effected without departingfrom the spirit and scope of the novel concept of the disclosure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of ahydraulic motor-pump assembly constructed in accordance with theprinciples of the present invention.

FIGS. 2, 3 and 4 are cross-sectional views taken along lines lI-II,iii-III and IV--IV in FIG. I.

FIG. 5 is a cross-sectional view of another embodiment of a hydraulicmotor-pump assembly constructed in accordance with the principles ofthis invention.

FIG. 6 is similar to FIGS. 1 and 5 and illustrates yet anotherembodiment of a motor-pump assembly constructed in accordance with thepresent invention.

FIGS. 7-10 are cross-sectional views taken along line VII- VII,VIII-VIII, IX-IX and X-X in FIG. 6.

FIG. I 1 is a cross-sectional view of a vehicular motor-drivearrangement including a hydraulic motor-pump assembly similar to that asshown in FIG. 1., the housing of the assembly being connected fast tothe frame of the vehicle and the shaft of the assembly rotatablymounting a wheel.

FIG. 12 is a cross-sectional view of another vehicular motor-drivearrangement in which the wheel is mounted on the housing of themotor-pump assembly and the shaft is connected fast to the frame of thevehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1-5, ahydraulic motor-pump assembly constructed in accordance with theprinciples of the present invention is indicated generally at referencenumeral I0. The assembly 10 comprises a housing 11 having a body portion12, an annular spacer member 13 and an end cap 14. An end wall 16 of thebody 12 faces a spaced parallel end wall 17 of the end cap 14 which,together with a cylindrical wall 18 of the spacer member 13, forms acylindrical chamber 19 within the housing 11.

A work input-output shaft 20 is joumaled in the housing 1 I by means ofbearing assemblies 21 and 22 and is axially aligned with the chamber 19.When the assembly 10 is being utilized as a pump the shafi 20 may beconnected to suitable drive apparatus and serves as a work input shaft.On the other hand when the assembly 20 is being utilized as a motor theshah 20 may be coupled to suitable driven apparatus and serves as a workoutput shaft. An outer end 23 of the shaft 20 may be splined as at 24 orotherwise adapted for suitable connection to the driving or drivenapparatus. A suitable seal assembly as indicated at reference numeral 26is provided near the outboard end of the shaft 20 to prevent loss offluid from the housing 1 1 past the shaft 20.-

of the invention illustrated in FIGS. 1-5,

Disposed within the chamber 19 is a gear set indicated generally atreference numeral 27 which, when the assembly is being utilized-as ahydraulic pump, is operated by the shaft 20 to increase fluid pressurethereacross. Conversely, when the assembly 10 is being utilized as ahydraulic motor drive pressurized fluid acts on the gear set 27 torotate the work output shaft 20.

The gear set 27 comprises a pair of gear members 28 and 29. The gearmember 28 is mounted fast to the shaft 20 for joint rotation therewithby means of a spline connection including a splined portion 30 of theshaft 20 and a splined bore 31 of the gear member 28. Formed on an outerwall 32 of the gear 28 are a series of gear teeth 33 which, in theembodiment are six in number. Since the gear member 28 rotates on afixed axis it is conveniently referred to herein as a rotor.

The gear member 29 surrounds the rotor 28 in the chamber 19 andcomprises an inner cylindrical wall 34 and an outer cylindrical wall 36.A series of cylindrically shaped recesses 37 are formed in the innerwall 34 and disposed within each is a tubular member 38. Since the wallsof the recesses 37 envelop the periphery of the tubular members 38through an are greater than 180 the members 38 are securely maintainedwithin their respective recesses 37.

The tubular members 38 serve as gear teeth for the gear member 29 andare greater in number by one than the teeth 33 of the rotor 28. Becauseof this difference in number between the teeth 33 of the rotor 28 andthe mating teeth 38 of the gear member 29 rotation of the rotor 29 aboutits fixed axes has the effect of causing the gear member 29 to move inan orbital fashion about the rotor 28 or both orbit and rotate about theaxis of the rotor 28. As a result of this orbital path of travel theouter gear member 29 is conveniently referred to herein as a statorassembly. Gear sets employing an externally toothed gear member and aninternally toothed gear member surrounding the externally toothedmember, in which the number of internal teeth exceeds by one the numberof external teeth, are often referred to by those skilled in the art asgerotor gear sets, one of the peculiar characteristics of which involvesthe relative movement thereof whereby, upon rotation of either one, thegear members both orbit and rotate relative to one another. The ratio ofrelative orbital speed to rotational speed of the gear members is equalto n+1, where n equals the number of external teeth of the inner gearmember.

In the embodiment illustrated in FIGS. 1-5 the stator assembly 29 of thegerotor gear set 27 comprises a series of gear teeth 39 found on theouter peripheral wall 36 thereof. A cooperating series of teeth 40 isformed on the cylindrical wall 18 of the spacer portion 13. The numberof teeth 40 exceeds the number of teeth 39'to the end that, as thestator assembly 29 orbits about the rotor 28, that is, as the axis ofthe stator assembly 29 moves about the axis of the rotor 28 in acircular path of travel, the stator assembly 29 will also rotaterelative to the housing 1 l.

In the embodiment illustrated the gear teeth 39 equal 52 in numberwhereas the gear tee h 40 equal 54 in number. Thus for each completemovement of the stator assembly 29 through an orbital path of travel thestator assembly 29 will rotate in the housing 11 two fifty-fourths orone twentyseventh of a revolution about its own axis.

As the gear members 28 and 29 rotate and orbit relative to one anotherthe gear teeth 33 and 38 form sequentially alternately expanding andcontracting fluid pockets between the teeth 38 of the stator assembly29. These fluid pockets are indicated respectively in F IG. 3 atreference characters 4l,4l,.

To illustrate this principle, assume the rotor 28 is rotated in acounterclockwise direction as indicated by the arrow 42 in FIG. 3. Thefluid pocket 41, will thereby be contracted or reduced in volume fromthat which would be indicated in FIG. 3. Similarly fluid pockets 4], and41,. would tend to become reduced in volume.

On the other hand fluid pockets 41,, 41, and 41 would tend to increasein volume. Fluid pocket 41, would tend to vary little in volume untilthe rotor 28 had turned through a substantial number of degrees sincethe gear tooth 33 disposed therewithin initially varies its positioninitially at a slower rate than the remaining gear teeth 33.

Meanwhile such counterclockwise rotation of the rotor 28 causes thestator assembly 29 to tend to orbit in a clockwise direction at anorbital speed six times greater than the rotational speed of the rotor28. However, as the stator assembly 29 orbits in a clockwise directionthe gear teeth 39 and 40 cause rotation of the stator assembly 29 in acounterclockwise direction.

Thus in the disposition of the parts shown in FIG. 3, for each completerevolution of the rotor 28 about its axis the stator assembly 29 willorbit six times, and for each movement of the stator assembly 29 throughone complete orbital path of travel it will rotate one twenty-seventh ofa revolution about its axis relative to the housing 11. The fluid whichacts upon or is acted upon by the hydraulic motor-pump assembly 10enters and leaves the housing 11 through a pair of openings indicated atreference numerals 43 and 44, both of which may be threaded toconveniently receive suitable fluid conduits. When the assembly 10 isbeing utilized as a motor the direction of rotation of the work outputshaft 20 will be determined by which of the openings 43 and 44 isconnected to the high-pressure side of the main fluid power pump andwhich is connected to the low-pressure side of the main pump. Thedirection of rotation of the shaft 20 may be reversed simply byreversing the connections of the openings 43 and 44 to the main powerpump.

On the other hand when the assembly 10 is being utilized as a hydraulicpump the direction of rotation of the work input shaft 20 determineswhich of the openings 43 and 44 will receive the low-pressure fluid andwhich will discharge the higher pressure fluid to the intended point ofuse.

When the assembly 10 is being utilized as a hydraulic motor it isnecessary that the high-pressure fluid be directed to the expandingfluid pockets 41,41, whereas when the assembly 10 is being utilized as aa pump the contracting fluid pockets communicate with that one of theopenings 43 and 44 delivering the high-pressure fluid from the assembly10. The fluid acting upon or being acted upon by the motor-pump assembly10 is directed to and from the expanding and contracting fluid pockets41,41, in timed relation to the rotational and orbital movement of thegear members 28 and 29 by means including the stator assembly 29 andreferred to generally as commutation means. The fluid such as oil or thelike is conducted by means of fluid passages 43, and 44, from theopenings 43 and 44 to a pair of annularly shaped grooves 43, and 44,formed in the radial wall 16 of the chamber 19. The grooves 43, and 44,are separated from each other by a ridge or land 46 as shown in H68. 1and 2.

The stator assembly 29 comprises a stator member 19,, the axialdimension of which corresponds to the axial dimension of the rotor 28and of the tubular members 38, and a spacer plate 29,. The spacer plate29, is firmly secured to the stator 29, by means of a plurality ofsuitable fasteners such as rivets indicated at reference numeral 47. Oneradial wall 48 of the spacer plate 29, engages in sliding relation withthe radial wall 16 of the housing body member 12 whereas an oppositewall 49 abuts an adjacent sidewall 50 of the stator member 19, andengages in sliding relation a corresponding sidewall 51 of the rotor 28.

Since the spacer plate 29, moves jointly with the stator member 29, itis apertured as 52 to accommodate orbital movement around the shaft 20.The diameter of an outer peripheral wall 53 of the spacer plate 29, issubstantially the same as the diameter of the outer wall 36 of thestator member 29,.

The fluid is communicated from the annular grooves 43, and 44, to thefluid pockets 41,41, by fluid passage means including a series ofangularly spaced apertures 54,-54 which extend axially through thespacer plate 29,. Communicating with the apertures 54,-54, are acorresponding number of elongated curved fluid flow passageways 56,-56,which are formed in the face of the end wall 50 of the stator member29,, and open respectively to their corresponding fluid pockets 41 -41through ports 57 -57,.

The triangularly shaped apertures 54 -54, are angularly offset fromtheir respective ports 57,-57, (and thus the fluid pockets 41 -41, withwhich they respectively communicate) by about 90 with respect to theaxis of the stator assembly 29. This angularly oflset relation serves toprovide the commutation system referred to herein as "phase-shift"commutation.

To further explain, reference is made to the relative disposition ofparts shown in FIGS. 3 and 4 wherein the axis of the stator assembly 29is vertically aligned with respect to the axis of the rotor 28. Assumingthat the motor-assembly is being utilized as a hydraulic motor and thatthe shaft is to be rotated in the direction indicated by the arrow 42,the pressurized fluid from the discharge side of the main power pump towhich the assembly 10 is connected will be coupled to the fluid opening43 and the return side of the main power pump coupled to the fluidopening 44. The groove 43, is therefore subjected to high pressure fluidand the groove 44, subjected to low pressure fluid.

In the position of the parts shown in FIGS. 3 and 4 the stator assembly29 must orbit counterclockwise to rotate the shaft 20 counterclockwise,and to accomplish this result it is preferable for the commutationsystem to provide for communication of all of the fluid pockets on theright-hand side of the axis of the stator assembly 29 (all of theexpanding fluid pockets 41 -41,) with high pressure fluid to applymaximum motive forces to the stator assembly 29, and as a resultthereof, to the rotor 28.

Phrased differently, maximum force is applied to the stator assembly 10when all of the fluid pockets 41,-41, located on one side of a lineextending through the axis of the rotor 28 and the point at which thestator assembly 29 contacts the cylindrical wall 18 of the chamber 19communicates with high-pressure fluid and all of the remaining fluidpockets 41,-41 communicate with low-pressure fluid.

In FIG. 3 the grooves 43, and 44, and the land 46 have been indicated inphantom lines to indicate the relative positions thereof when the statorassembly 29 is in the uppermost position thereof as shown in FIGS. 3 and4. Since the relative orbital movement and relative positions of thestator assembly 29 and the stationary grooves 43, and 44, determinewhich of the grooves 43, and 44, communicates with each of the fluidpockets 41,-41, (and accordingly the ports 57,,-57,) and thetriangularly shaped apertures 54,-54, in the spacer plate 29, (referredto herein as phase-shift" commutation) assures maximum input, output andefficiency of the motor-pump assembly 10.

The embodiment illustrated in FIG. 5 is similar to that shown in FIGS.l-4, the principal differences being that the lowand high-pressure fluidare supplied to and discharged from both of the axially spaced ends ofthe fluid pockets, rather than from only the right end of the pockets asobtains in the FIG. 1-4 embodiment. Since many of the individual partsof the embodiment shown in FIG. 5 are similar or identical tocorresponding parts shown in FIGS. 1-4 the same reference numerals willbe used for corresponding parts only increased by the number 100.

Thus in FIG. 5 the motor-pump assembly 100 comprises a pair of fluidopenings 143 and another pair of fluid openings 144. Each of the fluidopenings 143 communicates through a corresponding passage 143, to anannular groove 143,, one of which is formed in the radial wall 116 ofthe body member 112 and the other of which is formed in the radial wall117 of the housing end cap 1 14.

The stator assembly 129 includes a single stator member 129,, but a pairof spacer plates 129, are located respectively on opposite sides of thestator member 129 A series of triangularly shaped apertures 154,-154,are formed in each of the spacer plates 129, and a series of elongatedfluid flow passages 156 -156, are fonned in each of the end walls 150and 150' of the stator member 129,.

The provision of the dual fluid openings 143 and 144, the two sets ofgrooves 143, and 144, as well as the duplication of the other portionsof the commutation means serve to reduce pressure losses through theassembly 10, increase overall effciency and performance characteristicsand reduce wear and prolong the useful life of the assembly 10 byaxially balancing the fluid pressure generated forces acting on thegerotor gear set 127.

Another embodiment of a hydraulic motor-pump assembly constructed inaccordance with the principles of the present invention is illustratedin FIGS; 6-10 wherein reference numerals indicating parts similar tothose included in the former two embodiments are indicated by similarreference numerals in the 200" series.

In the embodiment shown in FIGS. 6-10 the stator assembly 229 comprisesa stator member 229, and a pair of spacer members 229, disposed onaxially opposite sides of the stator member 229,. Sandwiched in betweenthe stator member 229,, and the pair of spacer plates 229, are a pair ofstator plates 229,. The stator plates 229,. are securely fastened to thestator member 229,, by a plurality of fasteners as indicated on thereference numeral 58.

In this embodiment the apertures in the spacer plate 229, which registeralternately with the highand low-pressure grooves 243, and 244, areflatter and more circumferentially elongated than the triangularapertures 54,-54, of the FIG. l-4 embodiment. Furthermore the elongatedfluid flow passageways 256,, and 256, are formed in the faces of flatradial walls 59, 59 of the stator plates 229,, 29,, rather than in theface or faces of the stator member 229,

Furthermore the ports 257,-257, which communicate with the expanding andcontracting fluid pockets 241,-241, are formed in radial walls 60, 60 ofthe stator plates 229,, 229,, rather than in the inner wall 34 of thestator member 29,, as is found in the FIG. l-4 embodiment.

The fluid openings 243 and 244 are found in the end cap 214 rather thanin the body portion 212 and communicate with the annular grooves 243,and 244, formed in the radial wall 217 of the end cap 214.

Another pair of grooves 243, and 244, are formed in the face 216 of thebody portion 212. The two outer grooves 243, communicate with oneanother between the outer peripheral wall of the stator assembly 229 andthe cylindrical wall 218 of the chamber 219.

The pair of reduced diameter grooves 244, communicate with one anotherthrough a series of radially extending passageways 61 also formed in theradial walls 216 and 217 of the body portion 212 and the end cap 214 andradial passages 62 and an interconnecting axial passage 63 formed in theinput-output shaft 220.

Thus the embodiment shown in FIGS. 6-10 includes commutation means fordirecting the highand low-pressure fluid to and from the expanding andcontracting fluid pockets 241 -241, from axially opposite sides of therotor 228 and the stator member 229,, even though there is only a singlepair of fluid openings 243 and 244. In addition, the fluid is directedinto and out of the fluid pockets 241 -241, axially through the axiallyfacing ports 257,457,, rather than the radially facing ports 57 -57,, ofthe FIG. 1-4 embodiment.

FIG. 11 discloses an embodiment of the hydraulic motorpump assemblyshown in FIGS. 1-4 adapted for utilization in a vehicular drive system.A portion of the frame of the vehicle on which the assembly 10 ismounted is indicated at reference numeral 66, and the end cap 14 issecured fast to the frame 66 by means of a plurality of suitablefasteners such as the nuts and bolts indicated at 67 and 68respectively.

The shaft 20, which in this application serves as a work-output shaft,is slightly axially tapered as indicated at 69 and keyed as at 70 toreceive the hub 71 of a wheel 72 of the vehicle. The fluid openings 43and 44 are connected to the highand low-pressure sides of a main powerfluid pump, preferably through a valving mechanism enabling thedirection of rotation of the shaft 20 to be reversed without reversingthe operating direction of the main power pump. Accordingly,

when the assembly 10 is connected to the main pump the wheel 70 will berotated relative to the frame 66 b6 virtue of the relative orbital androtational movement of the gears of the gerotor gear set 27 and as aresult of the rotation of the shaft 20.

FIG. 12 is expositive of another embodiment of a hydraulic motor-pumpassembly constructed in accordance with the principles of the presentinvention and utilized in a vehicular drive system. Since many of thecomponents of the motorpump assembly correspond'closely or identicallyto those' found in FIGS. 14 such corresponding parts or components willbe given similar reference numerals although increased to the 300"series.

In this embodiment the housing 31 I of the motor-pump assembly 310 issecurely connected to the rim 371 of the vehicular wheel 372 by virtueof a plurality of fasteners indicated at reference numerals 73. On theother hand the shaft 320, through an extension 74 thereof, is securelyfastened to the vehicular frame 366, whereby the shaft 320 is maintainedin a fixed or stationary relation with respect to the frame 366.

Thus in the FIG. 12 embodiment of the invention the housing 311 rotateson a fixed axis rather than the shaft 320, which remains stationary. Thefluid openings 343 and 344, rather than being formed in the rotatinghousing 311, are formed in the extension 74 of the fixed shaft 320, andcommunicate by virtue of fluid passages 76 and 77 formed in the shaft320 and corresponding passages 78 and 79 formed in the body portion 312to the annular grooves 343,, and 344,, formed in the radial wall 16 ofthe body portion 312.

It will be appreciated by those skilled in the art that all of thevarious embodiments of the motor-pump assembly disclosed herein aresuitable for use in the vehicular drive arrangement as disclosed inFIGS. 11 and 12. In addition, of course, all of the illustratedembodiments may be advantageously utilized in a wide variety of fieldsof use.

What we claim is: l. A hydraulic pump-motor assembly comprising ahousing having means forming a gear chamber therein and a shaftjournaled thereon extending into said chamber,

a gear set in said chamber including an externally toothed rotor mountedfast on said shaft and an internally toothed stator assembly surroundingsaid rotor and orbitally and rotationally movable relative thereto toform alternately expanding and contracting fluid pockets between theteeth of said stator assembly, fluid-conducting means for communicatinghighand lowpressure fluid to said chamber, means formed on said statorassembly and on said housing for restraining said stator assemblyagainst rotation at the rotational speed of said rotor and for guidingsaid stator assembly in said orbital movement, and phase-shiftcommutation means including said stator assembly disposed in saidchamber for directing fluid between said fluid conducting means and saidexpanding and contracting pockets in response to orbital and rotationalmovement of said stator assembly relative to said rotor, saidchamber-forming means comprising a stationary radial wall, said statorassembly comprising a radial wall. in sliding engagement with saidchamber radial wall, and

said phase-shift commutation means comprising a pair of radially spacedconcentric annular grooves formed in the face of the stationary radialwall of said chamber in axial alignment with said shaft and a series ofports formed in the radial wall of said stator assembly and arranged ina circular pattern to register sequentially and alternately with saidgrooves in response to orbital movement of said stator assembly.

2. The invention as defined in claim 1, said stator assembly comprisinga stator member having a circumferentially continuous inner wall onwhich the teeth of said stator assembly are formed, said phase-shiftcommutation means further including a series of ports formed in saidinner wall and communicating respectively with said fluid pockets andmeans communicating said inner wall ports and said radial wall ports.

3. The invention as defined in claim 1, said stator assembly comprisinga stator member having a radial wall and a plate member fastened to theradial wall, and

means forming a series of ports in the face of the radial wall of saidplate member communicating respectively with the fluid pockets formedbetween the teeth of said stator member.

4. The invention as defined in. claim 1, said chamber forming meanscomprising another stationary radial wall in spaced parallel relation tosaid first mentioned radial wall, said stator assembly comprisinganother radial wall in sliding engagement with said other chamber radialwall, said phase-shift commutation means comprising another pair ofradially spaced annular grooves formed in the face of said other chamberwall and another series of ports formed in the other stator assemblyradial wall to provide dual fluid-directing means into and out of saidfluid pockets.

5. The invention as defined in claim 1, said gear chamber forming meanscomprising a cylindrical wall and said stator assembly comprising anouter peripheral wall, said stator assembly restraining means comprisingcooperating gear teeth formed on said cylindrical wall and on saidperipheral wall,

the number of gear teeth on the peripheral wall of said stator assemblybeing less than the number of gear teeth on said cylindrical wall.

6. A hydraulic pump-motor assembly comprising a housing having meansincluding a stationary radial wall for forming a gear chamber a shaftjournaled for rotation on a fixed axis and extending into said gearchamber,

a fluid inlet opening and a fluid outlet opening formed in saidpump-motor assembly,

gear set in said gear chamber including an externally toothed rotormounted on said shaft for joint rotation therewith on said fixed axisand an internally toothed sta' tor assembly surrounding said rotor andmovable orbitally and rotationally relative thereto to provide a seriesof sequentially alternately expanding and contracting fluid pocketsbetween the internal teeth of said stator assembly, meansinterconnecting said stator assembly and said housing for restrainingsaid stator assembly against.

rotation at the rotational speed of said rotor and for guiding saidstator assembly in said orbital movement, means including first andsecond radially spaced concentric annular grooves formed in the face ofsaid stationary radial wall and communicating respectively with saidfluid inlet opening and said fluid outlet opening, and fluid commutationmeans including said stator assembly for communicating said expandingfluid pockets with one of said grooves and said contracting fluidpockets with the other of said grooves during relative orbital androtational movement of said rotor and said stator assembly.

7. The invention as defined in claim 6, wherein said fluid commutationmeans comprises a plurality of fluid passage means each of whichterminates at one end at a first port opening to a corresponding one ofsaid fluid pockets and at an opposite end at a second port communicablealternately with said first and second grooves,

said first and second ports of each of said fluid passages being aboutangularly offset from one another with respect to the axis of the rotor.

8. The invention as defined in claim 7 wherein said stator assemblycomprises a radial wall in sliding engagement with the radial wall ofsaid housing and wherein said second ports are formed in the face ofsaid stator assembly radial wall.

9. The invention as defined in claim 7 wherein said stator assemblycomprises a stator member having a radial wall facing said gear chamberradial wall and a spacer plate fastened in fixed assembly to said statormember,

said second ports being formed in said spacer plate and said fluidpassage means comprising means forming bores in said spacer plateextending axially therethrough and communicating respectively with saidsecond ports.

10. The invention as defined in claim 9 wherein said fluid passages areformed in the face of the radial wall of said stator member and whereinsaid stator member comprises an inner peripheral wall on which the teeththereof are formed and in which said first ports are located.

11. The invention as defined in claim 7 wherein said stator assemblycomprises a stator member having a radial wall facing said gear chamberradial wall, a stator plate fastened to the radial wall of said statormember and a spacer plate fastened to said stator plate opposite saidstator member,

said second ports being formed in the face of said spacer plate adjacentsaid gear member radial wall and said first ports being formed in theface of said stator plate adjacent said stator member,

said fluid passage means comprising means forming bores in said statorplate and in said spacer plate corresponding to and communicating withsaid first and second bores respectively and means forming a pluralityof elongated fluid flow passages in the face of the radial wall of saidstator plate abutting said spacer plate each communicating a statorplate bore and a corresponding spacer plate bore.

l i i

1. A hydraulic pump-motor assembly comprising a housing having meansforming a gear chamber therein and a shaft journaled thereon extendinginto said chamber, a gear set in said chamber including an externallytoothed rotor mounted fast on said shaft and an internally toothedstator assembly surrounding said rotor and orbitally and rotationallymovable relative thereto to form alternately expanding and contractingfluid pockets between the teeth of said stator assembly,fluid-conducting means for communicating high- and low-pressure fluid tosaid chamber, means formed on said stator assembly and on said housingfor restraining said stator assembly against rotation at the rotationalspeed of said rotor and for guiding said stator assembly in said orbitalmovement, and phase-shift commutation means including said statorassembly disposed in said chamber for directing fluid between said fluidconducting means and said expanding and contracting pockets in responseto orbital and rotational movement of said stator assembly relative tosaid rotor, said chamber-forming means comprising a stationary radialwall, said stator assembly comprising a radial wall in slidingengagement with said chamber radial wall, and said phase-shiftcommutation means comprising a pair of radially spaced concentricannular grooves formed in the face of the stationary radial wall of saidchamber in axial alignment with said shaft and a series of ports formedin the radial wall of said stator assembly and arranged in a circularpattern to register sequentially and alternately with said grooves inresponse to orbital movement of said stator assembly.
 2. The inventionas defined in claim 1, said stator assembly comprising a stator memberhaving a circumferentially continuous inner wall on which the teeth ofsaid stator assembly are formed, said phase-shift commutation meansfurther including a series of ports formed in said inner wall andcommunicating respectively with said fluid pockets and meanscommunicating said inner wall ports and said radial wall ports.
 3. Theinvention as defined in claim 1, said stator assembly comprising astator member having a radial wall and a plate member fastened to theradial wall, and means forming a series of ports in the face of theradial wall of said plate member communicating respectively with thefluid pockets formed between the teeth of said stator member.
 4. Theinvention as defined in claim 1, said chamber forming means comprisinganother stationary radial wall in spaced parallel relation to said firstmentioned radial wall, said stator assembly comprising another radialwall in sliding engagement with said other chamber radial wall, saidphase-shift commutation means comprising another pair of radially spacedannular grooves formed in the face of said other chamber wall andanother series of ports formed in the other stator assembly radial wallto provide dual fluid-directing means into and out of said fluidpockets.
 5. The invention as defined in claim 1, said gear chamberforming means comprising a cylindrical wall and said stator assemblycomprising an outer peripheral wall, said stator assembly restrainingmeans comprising cooperating gear teeth formed on said cylindrical walland on said peripheral wall, the number of gear teeth on the peripheralwall of said stator assembly being less than the number of gear teeth onsaid cylindrical wall.
 6. A hydraulic pump-motor assembly comprising ahousing having means including a stationary radial wall for forming agear chamber, a shaft journaled for rotation on a fixed axis andextending into said gear chamber, a fluid inlet opening and a fluidoutlet opening formed in said pump-motor assembly, a gear set in saidgear chamber including an externally toothed rotor mounted on said shaftfor joint rotation therewith on said fixed axis and an internallytoothed stator assembly surrounding said rotor and movable orbitally androtationally relative thereto to provide a series of sequentiallyalternately expanding and contracting fluid pockets between the internalteeth of said stator assembly, means interconnecting said statorassembly and said housing for restraining said stator assembly againstrotation at the rotational speed of said rotor and for guiding saidstator assembly in said orbital movement, means including first andsecond radially spaced concentric annular grooves formed in the face ofsaid stationary radial wall and communicating respectively with saidfluid inlet opening and said fluid outlet opening, and fluid commutationmeans including said stator assembly for communicating said expandingfluid pockets with one of said grooves and said contracting fluidpockets with the other of said grooves during relative orbital androtational movement of said rotor and said stator assembly.
 7. Theinvention as defined in claim 6, wherein said fluid commutation meanscomprises a plurality of fluid passage means each of which terminates atone end at a first port opening to a corresponding one of said fluidpockets and at an opposite end at a second port communicable alternatelywith said first and second grooves, said first and second ports of eachof said fluid passages being about 90* angularly offset from one anotherwith respect to the axis of the rotor.
 8. The invention as defined inclaim 7 wherein said stator assembly comprises a radial wall in slidingengagement with the radial wall of said housing and wherein said secondports are formed in the face of said stator assembly radial wall.
 9. Theinvention as defined in claim 7 wherein said stator assembly comprises astator member having a radial wall facing said gear chamber radial walland a spacer plate fastened in fixed assembly to said stator member,said second ports being formed in said spacer plate and said fluidpassage means comprising means forming bores in said spacer plateextending axially therethrough and communicating respectively with saidsecond ports.
 10. The invention as defined in claim 9 wherein said fluidpassages are formed in the face of the radial wall of said stator memberand wherein said stator member comprises an inner peripheral wall onwhich the teeth thereof are formed and in which said first ports arelocated.
 11. The invention as defined in claim 7 wherein said statorassembly comprises a stator member havIng a radial wall facing said gearchamber radial wall, a stator plate fastened to the radial wall of saidstator member and a spacer plate fastened to said stator plate oppositesaid stator member, said second ports being formed in the face of saidspacer plate adjacent said gear member radial wall and said first portsbeing formed in the face of said stator plate adjacent said statormember, said fluid passage means comprising means forming bores in saidstator plate and in said spacer plate corresponding to and communicatingwith said first and second bores respectively and means forming aplurality of elongated fluid flow passages in the face of the radialwall of said stator plate abutting said spacer plate each communicatinga stator plate bore and a corresponding spacer plate bore.